The "accursed thing" was anything in Jericho other than the metallic vessels, which were to be taken "into the treasury of the LORD" (Joshua 6:19). All else was to be "accursed," literally "devoted" to God--that is, offered up to the Lord rather than kept for personal gain (Joshua 6:17). This was accomplished by burning the city to the ground--a great burnt offering. Achan, however, "coveted" and "took" some of the valuables for himself (Joshua 7:21), thus inhibiting God's continued blessing on the Canaanite campaign until the sin could be eliminated from the camp.